drbd: Do not Oops when C_STANDALONE when uuid gets generated

Got introduces with

commit 0c3f3451
Author: Philipp Reisner <philipp.reisner@linbit.com>
Date:   Mon May 17 16:10:43 2010 +0200

    drbd: Create new current UUID as late as possible
Signed-off-by: NPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: NLars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

drivers/block/drbd/drbd_main.c

@@ -1354,7 +1354,10 @@ static int w_new_current_uuid(struct drbd_conf *mdev, struct drbd_work *w, int c
 {
 	if (get_ldev(mdev)) {
 		drbd_uuid_new_current(mdev);
-		drbd_send_uuids(mdev);
+		if (get_net_conf(mdev)) {
+			drbd_send_uuids(mdev);
+			put_net_conf(mdev);
+		}
 		drbd_md_sync(mdev);
 		put_ldev(mdev);
 	}